The Internet Archive's Open Library project is making thousands of library records freely available for anyone's use. You can help build the Open Library by contributing your library's records, or persuading your favorite library to upload theirs.
Library catalogs that have already been uploaded include the San Francisco Public Library, the Library of Congress, Harvard University's HOLLIS catalog, and the University of North Carolina Library.
Check out the Open Library's requirements for guidelines on uploading your data.
MARC records, library card catalog records, bulk download downloadable